FIG. 1A is a perspective view of an superstructure installed on a substructure of a aqueduct bridge, illustrating a state in which a channel having a U-shaped cross section is installed on a pier installed on the ground, and FIG. 1B and FIG. 1C are perspective views illustrating detailed examples of repair or reinforcement means and method of the aqueduct bridge shown in FIG. 1A.
A aqueduct bridge 100 consisting of an superstructure, such as a channel with a U-shaped cross-section, and a substructure, such as a pier, is generally constructed in a manner that the aqueduct bridge 100 is divided into several segments 10 supported by a pier 20 according to its length, so that the superstructure formed at a predetermined height from the ground surface. The pier is a kind of a columnar structure, and its lower portion is embedded a predetermined depth into the ground. In general, a pier foundation is formed at the lower edge of the embedded columnar structure. Accordingly, a load of the superstructure, e.g., the channel, is transferred to the ground via the substructure, e.g., the pier and its foundation, thereby securely supporting the superstructure by the substructure. Here, since an upper surface of the pier or a coping portion 30 is a structurally weak portion, the durability thereof is deteriorated over time, resulting in occurrence of cracks. If the cracks become severe, the upper surface of the pier or the coping portion 30 is eventually damaged so that the superstructure supported thereby may settle. If a timely repair or reinforcement work is not carried out, safety of the superstructure is severely endangered. There have been proposed several conventional methods for repair or reinforcement of such an upper surface of piers or a coping portion, as follows: 1) after an superstructure supported by piers, is first removed, an upper surface of the pier or a coping portion is repaired, and then an superstructure is reconstructed; 2) as shown in FIG. 1B, a reinforcing steel member 40, such as a separate H-beam or a steel plate, is additionally installed to the pier; and 3) as shown in FIG. 1C, additional piers are installed in the vicinity of the existing piers. However, the conventional problems have several problems. For example, the first proposed method is effective only in a case where the superstructure is too severely damaged to repair. Above all, this method has a problem that a considerable cost is required in removing and reconstructing the superstructure. According to the second method, even if the reinforcing steel member 40 is additionally installed, a reinforcing capability thereof deteriorates over time, so that the upper surface of the pier or the coping portion may be further severely damaged. The third method has problems that it is not easy to establish a construction road for transporting equipments required in additionally constructing a pier and to acquire an additional construction site, and a considerable cost is required for such additional construction work. Also, in a case where a bearing force of soil of the foundation ground is not sufficiently strong, the pier foundation cannot bear the load applied from the superstructure, resulting in settlement of the pier foundation due to the load transferred from the superstructure. Such settlement is generally in the form of differential settlement, which may seriously adversely affect safety of the superstructure. However, conventional repair or reinforcement methods of preventing the pier foundation from settlement have not yet been found to be satisfactory. One conventional solution to the settlement problem was that the superstructure was entirely or partially removed, a pier, including a new pier foundation, was constructed and a superstructure was then reconstructed.
FIG. 2A is a side view of an aqueduct bridge having a box-shaped superstructure 10 having a U-shaped cross section, installed on a pier 20 by a bearing 60. The superstructure 10, channel, is installed at a predetermined height above the pier 20. Because the pier 20 and the superstructure 10 is supported by a bearing force of soil of foundation ground, If the force of soil with respect to the ground is insufficient, the pier or the pier foundation settles and the superstructure also unavoidably settles. According to concentration of a load to connecting portion of a superstructure, eventually, as shown in FIG. 2B, the bearing 60 may be damaged or the upper surface of the pier (or the coping portion) may be damaged. Also, as the bearing 60 degrades, the pier coping portion is damaged, so that the superstructure may differentially settle, thereby the safety of the superstructure or the substructure is endangered. To overcome such a safety problem, by way of prevention of collapse of the superstructure or leakage of water flowing through the channel, one possible conventional way was to remove the superstructure itself before reconstructing a new pier. In order to repair or reinforce the coping portion of the pier or the bearing it is necessary to lift the superstructure. Here, even if the coping portion of the pier or the bearing is replaced after simply lifting the superstructure, an additional repair or reinforcement work is required unless a sufficient bearing force of soil of the foundation ground is acquired. Thus, when there is settlement in the pier foundation of the existing structure, a separate superstructure supporting means should be provided. In this case, the superstructure needs to be additionally supported by installing a new pier next to the pier on the ground. However, due to construction site conditions, a necessity of establishing a construction road for equipment delivery, various constructional difficulties resulting from the use of large-scale equipment, an increase in the construction cost, using the existing large-scale equipments and special-purpose equipments was very restricted.